What is the Google Mobile First Index?

Before you despair, keep in mind some things.

First, for now this is a practice of Google, is not a general rule, even Google representing 90% or more of the search market in Brazil is a practice of the company and not the W3C, so does not necessarily have the see directly with the developers, mainly for that develops systems etc.

Site Mobile (m) vs. Mobile First

Keep in mind that we have different concepts here! Mobile First would be roughly a site developed primarily as a mobile focus, it would actually be a mobile site that fits for large screens, not a large screen-driven website that fits into screens small. Maybe at the time of developing the main point is that medias queries use min-width and not max-width link

/* este estilo aplica-se a partir de 0px até 900px */
body {
      background: red;
} 

/* este estilo aplica-se a partir de 900px em diante */
@media ( min-width: 900px ) {
  body {
    background: green;
  }
}

A Site Mobile , or Site M is a "new" site, that is not a single site that fits the width of the screen, The truth is that there is another URL, other .html files, other .css, etc ... Although a Site M can have mobile first concepts, it is a different site and would be something like m.example.com.br other example.com.br

<link rel="canonical" href="https://example.com/">
<link rel="alternate" media="only screen and (max-width: 640px)" href="https://m.example.com/">

Google Recommendations

• Your mobile site needs to display the same content as your computer site.
• Structured data needs to be present on both versions of your site.
• Metadata must be present in both versions of the site.
• Check both versions of your site in Search Console to ensure that you have access to both of your data and messages.
• Check the links for separate URLs.
• Verify that the robots.txt
• Make sure you have the elements of the rel=canonical and rel=alternate correct link

Source: link

SEO

See what Google says:

  

In Google, there is a preference for content optimized for mobile devices in the indexing process.

So from the point of view of SEO in Google this means that if your competitors already have the mobile version, they can stay in front of you. In other words, Google tends to give preference to return results of Sites of type M in their searches.

This does not necessarily mean that your unique Responsive site will no longer be indexed by their crawler , it just means that it can improve the ranking of Sites M in search results. Even SERP may vary depending on whether the search was done from a Mobile or Desktop device. SERP: link

Source: link

Questioning

Point to think ... So that we have two sites if we only have one Site M, but that suits the Desktop, having only a URL m.example.com.br . What would Google's bot validation look like? What would be the result of SERP if the site only has a Version M ?

In terms of web design, the idea of mobile first for layout and design has been around for a long time, because today the pages are mostly accessed by mobile devices, so the mobile site is first created and, then desktop

If this already exists in site creation, why would not your indexing be any different? Basically, the Mobile First Index is indexing the web pages by its mobile version. This change will be gradual, there are already sites that are being indexed in this way, everyone has gone through this, but there is still a lot to do, does not mean that you should not worry, it is important to be aware of these changes and put them in practice

An important point is that the mobile page is as complete as possible, several sites have a full desktop version and a mobile one with lean content, which can affect indexing

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